Strength is usually compromised with toughness of polymer blends. We report a new way to synchronously strengthen and toughen a typical blend of epoxy resin/nitrile-butadiene rubber (EP/LNBR) with Janus nanosheets (JNs). The silica-based JNs contain a reactive epoxide group and nitrile-butadiene rubber on the opposite sides. They are robust of high strength and toughness. The JNs are covalently bound at the EP/LNBR interface upon blending and cross-linking, which can effectively transfer stress in between the two phases. At the saturation coverage of the interface with the JNs, mechanical properties of the blends reach the maxima. Excess JNs will stack into multiple layers at the interface, which will lead to interfacial slippage and thus to worse properties. This report may open a new avenue to achieve higher performance polymer materials by using Janus materials.

No abstract

No abstract

A novel kind of nanothermometer was prepared, which has potential to monitor the temperature variation in the nano regime. The nanothermometer was based on biocompatible fluorescent carbon nanodots (CDs) via one-step microwave assisted synthesis, and two kinds of polymers, including thermo-sensitive poly-(N-isopropylacrylamide) (PNIPAM) and non-thermo-sensitive polyethylene glycol (PEG), were used simultaneously to modify the CDs. Therefore, the as-prepared nanothermometer possesses a CD core and a mixed shell consisting of PEG and PNIPAM chains. The elaborately-designed nanostructure endows the nanothermometer with both temperature sensing capacity and the solution stability. When heating up above the lower critical solution temperature (LCST) of PNIPAM, hydrophobic phase transition occurred to PNIPAM, and the nanothermometer evolved into the core-shell-corona structure, with a freshly-formed and collapsed PNIPAM shell. Meanwhile, the fluorescence behavior of the nanothermometer changed along with the structure transition reversibly without fluorescence decay.The detection temperature of the nanothermometer is consistent with the LCST of the applied thermosensitive polymer passivating agents. Moreover, this nanothermometer can remain stable without aggregation and fluorescence quenching whether below or above the LCST due to the stabilizing effect of the PEG chains. Furthermore, the nanothermometer could be endocytosed by cells with negligible cytotoxic effects. In view of the excellent sensitivity and reversibility, preferable biocompatibility as well as nano-scale structure, this nanothermometer shows great potential applications in intracellular imaging and temperature sensing.

Thermo/pH dual responsive mixed-shell polymeric micelles based on multiple hydrogen bonding were prepared by self-assembly of diaminotriazine-terminated poly(ɛ-caprolactone) (DAT-PCL), uracil-terminated methoxy poly(ethylene glycol) (MPEG-U), and uracil-terminated poly(N-vinylcaprolactam) (PNVCL-U) at room temperature. PCL acted as the core and MPEG/PNVCL as the mixed shell. Increasing the temperature, PNVCL collapsed and enclosed the PCL core, while MPEG penetrated through the PNVCL shell, thereby leading to the formation of MPEG channels on the micelles surface. The low cytotoxicity of the mixed micelles was confirmed by an MTT assay against BGC-823 cells. Studies on the in vitro drug release showed that a much faster release rate was observed at pH 5.0 compared to physiological pH, owing to the dissociation of hydrogen bonds. Therefore, the mixed-shell polymeric micelles would be very promising candidates in drug delivery systems.